[ This set of files is an HTML version of a manuscript that was prepared sometime in mid 1980s, as working documents to help identify Papuasian pteridophytes. It is presented here essentially as it was at the time, and users should be aware that references and collections made over the last 14 years have not been added and that taxonomy and nomenclature has not been updated accordingly. An update is intended, as time permits. - jrc ]

KEYS TO THE PTERIDOPHYTES OF PAPUASIA

J.R. Croft

Introduction

The following keys cover the genera of ferns and fern allies recorded from Papuasia, the geographical area including the political units of Papua New Guinea, Irian Jaya and the Solomon Islands. All genera except Thayeria and Matonia, known from single collections from Irian Jaya, have been collected in Papua New Guinea; these two genera may turn up with more intensive collection; all genera known from the Solomon Islands are also known from Papuan New Guinea and the New Guinea mainland.

This is a complilation of keys from various sources. The basic architecture of the main key to families is that of Holttum (1959 - General key No. 1). This key was selected because it relies less heavily on the vasculature of the stipe than his Key No. 2, a character not readily evident in dried material, and works well both in the field and in the herbarium. It has been modified to exclude those genera known not to occur in Papuasia, and expanded to include the fern-allies, and to accommodate a few deficiencies of the original key when applied to the Papuasian flora. For purely practical reasons the families have been named in accordance with Holttum's arrangement of Pichi-Sermolli's system presented in the 8th edition of Willis' "Dictionary of the flowering plants and ferns" (Willis 1973).

In many instances pteridologists disagree over the allocation of genera to families and a complete resolution of these difference is unlikely in the near future. Some of the various alternatives are indicated in the notes after each family key.

For a sequential arrangement of the pteridophytes see Crabbe, Jermy and Mickel (1975). This arrangement has been adopted by several major herbaria, although controversy still exists over the rank and composition of some of the groups (e.g. Pichi Sermolli 1977; Brownsey et al. 1985).

The keys to genera are fundamentally those of Holttum (1959), expanded to include the improvements of subsequent revisions, and those genera added to the flora as a result of recent collections. The most notable contribution here is Holttum's elaboration of the Thelypteridaceae.

Bracketed keys have been used for the practical considerations of ease of format and conservation of space. In the long keys headings have been inserted to make the keys easier to use for those familiar with pteridophytes. Those who are unsure should follow through each step in turn.

The Pteridophytes of Papuasia

Terrestrial, epiphytic, rupestral or aquatic (not marine) vascular plants of mostly moderate stature with distinct alternating generations: the gametophyte small and relatively short-lived and avascular producing the sexual organs antheridia (male) and archegonia (female); the sporophyte the dominant generation, large and vascular, producing asexual spores which develop into the gametophyte.

In Papuasia there are 187 genera of pteridophytes covering c. 1700 - 1800 species; undescribed taxa may push this figure as high as 2000. Worldwide there are 9000 - 12000 species in c. 350 genera. The allocation of families is always a matter of dispute among pteridologists the number ranging from c. 60 to less than 10; this treatment divides the genera among 44 families, largely by treating all families in their narrowest sense.

The pteridophytes are generally considered to be an unnatural collection of several unrelated groups that should have equal status to the Bryophyta (mosses and liverworts) and the Spermatophyta (seed-plants). There are 4 such groups: Psilopsida (Psilotum and Tmesipteris); Lycopsida (Lycopodium, Selaginella, Isoetes); Sphenopsida (Equisetum); Filicopsida (true ferns). However, in this treatment, for purely practical purposes, these divisions are ignored.

The descriptions and keys in this treatment cover only the sporophyte generation, since this is the stage that most people see and are familiar with. The gametophyte and sexual stages of pteridophytes are for the most part small and short-lived, and although they certainly offer useful diagnostic characters, they have only been studied for a very small proportion of the species.

Note: In this key the numbers in parentheses after key couplet numbers indicate the preceding couplet, thus "49 [42]" means that a choice in couplet 42 lead to couplet 49. This is to enable checking by working backwards in confusing situations.

Key to families

[1] 2 - 3 (rarely
4) sporangia fused into a single synangium, and borne in the axils
of minute and bract-like or larger and leaf-like bifid sporophylls;
homosporous; axis not differentiated into roots...

Plants rooted in soil, mud, or on rocks, or on
floating mats of vegetation, sometimes some plants free-floating as
well; fronds large and pinnately divided; vegetative reproduction
sometimes by marginal proliferous buds

[9] High-climbing epiphytes starting
from the ground, uncommonly scrambling and thicket-forming in the
absence of trees; fronds pinnate, sterile with close parallel venation
with a single series of very narrow areoles along the midrib, fertile
very narrow and completely covered by sporangia

Ground ferns with radial or creeping rhizomes,
in one case thicket-forming but never epiphytic; fronds pinnatifid
to pinnately compound, veins freely anastomosing, or in pinnate groups,
anastomosing or not, sporangia borne in discrete or continuous sori
on non-contracted fronds, or if on contracted fronds, protected by
the reflexed margin of the lamina

Rhizome creeping, not radial, or if thin and radial
plants spreading by wiry stolons; venation in pinnate groups, free
or uniting, or reticulate with included free veinlets; sporangia borne
in discrete +/- round sori

Pinnae deeply or shallowly toothed, not articulate
to the rachis; veins in pinnate groups in the lobes, free or united
with veins of adjacent groups to form a single excurrent vein; plants
not stoloniferous, sometimes with proliferating buds along the rachis;
sori indusiate or not

[42] Caudex often massive, erect,
fleshy; stipes succulent with stipule-like outgrowths at their bases;
2 - 3-pinnate, bases of pinnae swollen; sporangia large and arranged
in two short adjacent rows along a vein, sometimes fused into a single
unit

[56] Fronds simply pinnate;
aerophores (projections of aerating tissue) at the base of the stipe,
sometimes also at the base of the pinnae; sori acrostichoid, densely
covering the entire lower surface of the contracted linear fertile
pinnae, all pinnae fertile.

[76] Rachis grooved on the upper
surface, the groove open to admit the groove of the midrib of the
pinnae (in species with simple, unlobed pinnae the edge of the rachis-groove
does not open to admit grooves of costae, the lamina not decurrent
along edge of rachis groove)